The present invention relates to turbine engine arrangements and more particularly to engines used with aircraft to provide propulsion.
Use of turbine engines to provide propulsion for aircraft is well known. The turbine engine provides thrust or movement of the aircraft and traditionally as shown in FIG. 1 an engine A is located within a nacelle B whereby the principal axis of the engine X—X is positioned in order to optimise aircraft performance in terms of fuel economy. Thus, thrust from the engine is in the direction of arrowhead C which is angled relative to the axis of motion (arrow J) in order to achieve best lift to drag characteristics. This relationship requires that the inlet duct D along with the nacelle B and hot/cold nozzle vectoring is orientated as shown in FIG. 1. In such circumstances, as can be seen in FIG. 1 there is a slight turn in the input flow in the direction of arrowheads E and E′ in order to align with the engine axis X—X. This turning diminishes performance.
The current practice depicted in FIG. 1 aligns the engine axis X—X which generates a proportion vector in the direction of arrowhead C which has a component of lift in a proportion that achieves best lift to drag ratios when in combination with an associated airframe F. Thus to provide the most favourable pressure intake performance recovery requires a scarfed (i.e. angled) front inlet duct D to the nacelle B in order to align the upwash in the front of a leading edge H of a wing G. This upwash is fundamental to a subsonic wing and exists to differing extents at almost all non aerobatic phases of flight. This scarfed inlet comprises a front end of the nacelle B which turns the airflow E in the direction of arrowhead E′ (dashed lines) into alignment with the engine axis X—X. Such turning of the airflow E in the direction of arrowhead E′ creates a pressure loss in the airflow into the engine A and so reduces efficiency.